Came across a question on Wowhead why the following macro wouldn’t work:
/cast [@mouseover,dead] Skinning
and upon testing it myself, I noticed that casting “Skinning” via macro casts/attempts to cast the spell with the ID 308569, a passive from Shadowlands, while right-clicking a skinnable corpse casts the spell with the ID 158756, apparently a WoD spell, but still being used.
Therefore, skinning via macro does not work. There is a short cast time, but I think that’s rather a sign of the cast failing/fizzling.
First tested this on an alt with only Shadowlands Skinning, but learned Dragon Isles Skinning and then switched to a character with Khaz Algar Skinning, nothing changed.
Googling shows that skinning via macro should work, possibly earlier this year still, so it might be a recent change that broke this.